Aromatic citrus oil concentrate which is stable in storage

ABSTRACT

Peel oil concentrate produced from cold-pressed citrus peel by adsorption at a solid separating agent which adsorbs polar organic substances or by extraction with a polar liquid solvent. The peel oil concentrate is a stabilizing agent for a natural citrus aroma concentrates.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional application of Ser. No. 362,893 filedon Mar. 26, 1982, now U.S. Pat. No. 4,435,437.

BACKGROUND OF THE INVENTION

The present invention relates to concentrates from natural citrus oilswhich are used to improve the taste and flavour of natural fruit juicesand fruit drinks made of citrus fruits.

Substances originating from natural fruits and applicable for theabove-stated uses are obtained during processing of most freshlyharvested fruits, initially as a raw material in the form of a peel oil,or an essence oil, or as aqueous essences. The substances are thenconcentrated further to increase their aromatic content and to separateundesirable substances. The raw materials are complicated mixtures ofsubstances, some of which are very thermolabile, which must beconsidered as the carriers of the desirable aromatic nuances. Thethermoability of the raw materials necessitates their storage only in afrozen state and necessitates shipping them from manufacturer toconsumer, i.e. generally the fruit drink producer, in chains offreezers. This requirement is expensive and considerably increases theprice of such drinks.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a peel oilconcentrate which is stable in storage.

A further object of the present invention is to provide such a peel oilconcentrate which is stable in storage and does not change or lose itsaroma even if stored for long periods of time (several weeks to severalmonths) at room temperature in pure form as well as in diluted form.

Another object of the present invention is to provide a natural citrusaroma concentrate which is stable in storage and does not change or loseits aroma even if stored for long periods of time (several weeks toseveral months) at room temperature.

Still another object of the present invention is to provide a processfor producing a peel oil concentrate.

Additional objects and advantages of the present invention will be setforth in part in the description which follows and in part will beobvious from the description or can be learned by practice of theinvention. The objects and advantages are achieved by means of thecompositions, processes, instrumentalities and combinations particularlypointed out in the appended claims.

To achieve the foregoing objects and in accordance with its purpose, thepresent invention provides a citrus peel oil concentrate produced fromcold-pressed citrus peel oil, the peel oil concentrate being obtained bysubjecting the cold-pressed citrus peel oil to adsorption at a solidseparating agent which adsorbs polar organic substances to thereby forman adsorbed fraction at the solid separating agent, eluting the adsorbedfraction with a polar organic eluant to form an eluate containing theadsorbed fraction, recovering the eluate, and separating the adsorbedfraction from the eluate.

In another embodiment of the present invention, the peel oil concentrateproduced from cold-pressed citrus peel oil is obtained by extracting thecold-pressed citrus peel oil with a polar organic solvent to form asolvent extract phase and a raffinate phase, separating the solventextract phase from the raffinate phase, and separating oil from theseparated solvent extract phase.

The peel oil concentrate obtained by either of the above process can beused as a stabilizing agent for a natural citrus aroma concentrate. Thenatural citrus aroma concentrate can comprise a mixture of the peel oilconcentrate and an essence oil concentrate, or a mixture of the peel oilconcentrate and a concentrate of an aqueous essence, or a mixture of thepeel oil concentrate, an essence oil concentrate and a concentrate of anaqueous essence. The natural citrus aroma concentrate retains its aromaand is stable in storage.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, but are notrestrictive of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is based on the observation that peel oil containssubstances which act as stabilizers. In the present invention, the peeloil is treated with the aid of suitable processes to form a peel oilconcentrate which contains an enriched amount of the stabilizingsubstances. The thus obtained peel oil concentrate can be utilized as astabilizing agent for natural citrus aroma concentrates.

To better understand the invention, a few definitions will now belisted:

1. "Peel oils" are understood to mean oils which are obtained in a coldway by pressing citrus fruit peel which has been freed from pulp.

2. "Essence oil" is understand to mean the oily phase which is obtainedduring condensation of the vapors escaping during concentration ofcitrus fruit juices.

3. "Aqueous essence" is understood to mean the aqueous phase whichdevelops during the condensation of the vapors escaping during theconcentration of citrus fruit juices.

4. "Citrus oil concentrate" or "natural citrus aroma concentrate" isunderstood to mean a mixture containing the peel oil concentrate of thepresent invention and at least one other concentrate such as anessential oil concentrate or concentrate of aqueous essence.

The problems with which the present invention is concerned generallyexist in connection with all citrus fruit products, including inparticular oranges, lemons, tangerines and grapefruit.

The manufacture of the peel oil concentrate is an important aspect ofthe present invention and results in a peel oil concentrate which isneeded for the stability in storage of the above-mentioned citrus oilconcentrate. In accordance with the present invention, it has beenobserved that the above-mentioned substances which act as stabilizerscan be recovered from citrus peel oil concentrated or can be enrichedtherein, if the cold-pressed citrus peel oil is conducted, in achromatographic column, through a solid separating agent which adsorbspolar organic substances to thereby form an adsorbed fraction at thesolid separating agent. Active silica gel has been found to beparticularly suitable as a solid separating agent. However, othercorrespondingly acting separating agents can also be used, for example,finely dispersed aluminum oxide. After transferring the starting peeloil to the chromatographic column and passing it through, the separatingagent is washed with a small amount of nonpolar solvent, for example,petroleum ether. Then, the adsorbed fraction is eluated with a polarorganic eluant, for example, ethanol, to form an eluate containing theadsorbed fraction. Other examples of suitable organic polar solvents areethyl-acetate, ethyl-ether or acetone. The eluate is recovered orseparated from the separating agent. The resulting recovered adsorbedfraction can then be separated from the eluate by, for example asaturated sodium chloride solution or by distillation. The so separatedadsorbed fraction is the peel oil concentrate of the present invention.

Adsorption in the chromatographic separating column has been found mosteffective. However, in accordance with another embodiment of the presentinvention, it is also possible to enrich the desired substances byliquid extraction with a polar organic solvent. The term "polar organicsolvent as used herein is understood to mean a single polar organicsolvent which comprises a chemically uniform substance, and alsomixtures of several polar organic solvents. Ethanol has been found to beparticularly suitable for the implementation of this liquid extractionprocess. Other solvents are ethyl-acetate, methanol, n-propanol,i-propanol or propylen-glycol.

In the liquid extraction process the cold pressed citrus peel oil isextracted with the polar organic solvent to form a solvent extract phaseand a raffinate phase. The solvent extract phase is then separated fromthe raffinate phase. The solvent extract phase contains the peel oilconcentrate which is then separated from the solvent extract phase, by,for example, a saturated sodium chloride solution.

With the above-mentioned methods, the stabilizing substances which arecontained in peel oils, i.e. tocopherols, carotinoides, lipoides,phosphorus lipides and similar group of substances, are enriched.Undesirable labile compounds of citrus products, such as monoterpenesand sesquiterpenes are separated to a substantial degree.

According to the present invention, the resulting peel oil concentrateis now mixed as required with essence oil concentrate, with concentrateof aqueous essence of with both to form a citrus oil concentrate. Thequantity of peel oil concentrate to be used in the citrus oilconcentrate depends on the degree of the desired stabilization as wellas on the fact whether the flavor of the fruit peel is to be emphasizedor not.

The citrus oil concentrates of the present invention have a great aromaimparting capability. Thus, 5 to 10 g of the citrus oil concentrate issufficient to impart aroma to 100 l fruit drink.

A preferred composition of the citrus oil concentrate of the presentinvention comprises 10 to 90 percent by weight citrus peel oilconcentrate obtained from cold-pressed citrus peel oil in theabove-described manner, that is, by adsorption at said separating agentswhich adsorb polar organic substances or by extraction with polar liquidsolvents. The remainder is essence oil concentrate.

Another preferred citrus oil concentrate composition according to thepresent invention includes 10 to 95% by weight citrus peel oil, producedin the above-described manner, the remainder concentrate of an aqueousessence.

A further preferred citrus oil concentrate composition according to thepresent invention includes 10 to 90 percent by weight citrus peel oilconcentrate, produced in the above described manner, 5 to 85 percent byweight essence oil concentrate, and 5 to 85 percent by weightconcentrate of an aqueous essence.

The following examples are given by way of illustration to furtherexplain the principles of the invention. These examples are merelyillustrative and are not to be understood as limiting the scope andunderlying principles of the invention in any way. All percentagesreferred to herein are by weight unless otherwise indicated.

EXAMPLE 1

This example illustrates the production of orange peel oil concentratewhich is stable in storage and has a preservative effect.

A glass tube having a diameter of 13 mm and a length of 1000 mm wasfilled with 35 g active silica gel. 200 g cold-pressed California orangepeel oil were conducted through the thus prepared separating column.After passage of the peel oil, the column was washed with 50 mlpetroleum ether. The column was then eluated with 150 ml of concentratedethanol containing 96 volume percent ethanol.

The resulting eluate was poured into 500 ml of a saturated aqueoussodium chloride solution which caused an oil to be separated. Aftersettling, the oil phase was separated from the aqueous phase, andapproximately 5 g orange peel oil concentrate was obtained as the oilphase.

The orange peel oil concentrate was analyzed and the following data wereobtained:

Density (D) at 20° C.=0.913 g/cm³

Index of refraction (n_(D)) at 20° C.=1.478

The composition of the orange peel oil concentrate was as follows:

31.8% aldehyde, calculated as decyl aldehyde

0.9% acid, calculated as acetic acid

16.6% ester, calculated as geranyl acetate

18.2% alcohol, calculated as linalool.

The orange peel oil concentrate was insoluble in 96% ethanol.

EXAMPLE 2

This example illustrates the production of grapefruit peel oilconcentrate which is stable in storage and has a preservative effect.

A glass tube having a diameter of 13 mm and a length of 1000 mm wasfilled with 35 g active silica gel. 200 g of cold-pressed grapefruitpeel oil were conducted through the thus prepared adsorption tube. Afterpassage of the oil through the tube, the tube was washed with 50 mlpetroleum ether. After drainage of the petroleum ether, the tube waseluated with 150 ml concentrated ethanol containing 96 volume percentethanol. The resulting eluate was collected and the ethanol wasdistilled out from the eluate using a reduced pressure of approximately20 mbar. Approximately 5 g grapefruit peel oil concentrate were obtainedas distilled residue. The grapefruit peel oil concentrate was analyzedand the following data were obtained.

Data:

D 20° C.=1.017 g/cm³

n_(D) 20° C.=1.52

The grapefruit peel oil concentrate was insoluble in 96% ethanol.

EXAMPLE 3

This example illustrates the production of lemon peel oil concentratewhich is stable in storage and has a preservative effect.

200 g lemon peel oil, whch is a cold pressed lemon peel oil, were filledinto a separating funnel having a volume of 500 ml. The oil was shakenout four times with ethanol. Each shaking employed 100 ml ethanolcontaining 73 percent by weight ethanol. The alcohol phase from eachshaking was separated, and the so separated alcohol phases were combinedwith each other. The combined alcohol phases were stirred into 800 ml ofa saturated sodium chloride solution, whereupon an oil separate. Aftersettling of the oil, and washing twice with 50 ml water each time, 22 gof lemon peel oil concentrate were obtained.

The lemon peel oil concentrate was analyzed and the following data wereobtained:

D 20° C.=0.860

n_(D) 20° C.=1.477

Solubility in 90% ethanol 1:3 this means: One Vol. Part of oil issoluble in 3 Vol. Part of ethanol of 90 Vol %.

The composite in the lemon peel oil concentrate was as follows:

12.7% aldehyde, calculated as decyl aldehyde

0.15% acid, calculated as acetic acid

5.8% ester, calculated as geranyl acetate.

EXAMPLE 4

This example illustrates the production of an orange essence oilconcentrate.

100 g orange essence oil were filled into a separating funnel having avolume of 200 ml. The oil was shaken out four times with ethanol. Eachshaking employed 50 ml ethanol containing 62 percent by weight ethanol.The alcohol phase from each shaking was separated, and the so separatedalcohol phases were combined with each other. The combined alcoholphases (extracts) were stirred into 500 ml saturated sodium chloridesolution whereupon an oil separated. After the oil settled, it wasrecovered in a known manner in an amount of 6 g.

The so recovered orange essence oil concentrate was analyzed and thefollowing data were obtained:

D 20° C.=0.857 g/cm³

n_(D) 20° C.=1.476

Solubility in 90% ethanol 1:1 this means: One Vol.-part of oil issoluble in 1 Vol.-part of ethanol of 90 Vol %.

The composition of the orange essence oil concentrate was as follows:

12.2% aldehyde, calculated as decyl aldehyde

0.1% acid, calculated as acetic acid

5.7% ester, calculated as geranyl acetate.

EXAMPLE 5

This example illustrates the production of a grapefruit essence oilconcentrate. 500 g grapefruit essence oil were filled into afractionating apparatus whose piston volume was 1000 ml, and which wasprovided with a fractionation attachment. Under reduced pressure of 20mbar, and cooling of the apparatus with liquid nitrogon, distillationwas initiated slowly by carefully raising the temperature. After 15 mlof distillate had been transferred, the distillation was terminated Thedistillate represented the desired grapefruit essence oil concentrate.It had the following data:

D 20° C=0.842

n_(D) 20° C=1.4705

Solubility in 90% ethanol 1:6 that means: One Vol.-part of the oil issoluble in 6 Vol.-parts of ethanol of 90 Vol %.

The grapefruit essence oil concentrate had the following composition:

3.17% aldehyde, calculated as decyl aldehyde

0.02% acid, calculated as acetic acid

3.0% ester, calculated as geranyl acetate.

EXAMPLE 6

This example illustrates the production of a concentrate of aqueousorange essence.

500 g aqueous orange essence were filled into a fractionating apparatushaving a piston volume of 1000 ml and a fractionating attachment. Byslowly distilling out the fraction transferred up to 85° C., 30 mldistillate were obtained. The distillate was the desired concentrate ofaqueous orange essence. It had the following data:

D 20° C.=0.813 g/cm³

n_(D) 20° C.=1.365

Solubility: clearly soluble in orange peel oil and water.

The concentrate of aqueous orange essence had the following composition:

5.6% aldehyde, calculated as decyl aldehyde

0.02% acid, calculated as acetic acid

0.46% ester, calculated as geranyl acetate.

EXAMPLE 7

To demonstrate keeping quality, the so-called "tocopheral test" wasused. Tocopherol (vitamin E) is known to be an extremely thermolabilesubstance which is present in numerous fruits and also is citrus fruits.Tocopherol can be determined by thin-film chromatography. Prefabricatedhigh resolution thin-film chromatography plates made by Merck,Darmstadt, were used to perform the comparison test selected here.

To perform the test, 20 μl of the substance to be examined were appliedto the high resolution chromatographic thin-film plate. Chloroform wasused as the mobile phase or fluxing agent which ascends the thin-filmplate and effects the separation. After accomplishing the separation,the plate was sprayed with a solution of one part antimony pentachloridein four parts chloroform. The spot of tocopherol then became visible ina reddish brown color.

Samples of various substances were subjected to the tests immediatelyafter being formed, and after storage at 20° C. for varying timeperiods. The results of the tests are set forth in the table below. The"+" designation indicates that tocopherol became visible in the test,whereas the "-" designation indicates that tocopheral did not becomevisible.

    ______________________________________                                                       After                                                          Substance Immediately                                                                              2 wks   3 mos.                                                                              6 mos.                                                                              9 mos.                               ______________________________________                                        Fresh orange                                                                            +          -       -     -     -                                    peel oil                                                                      Orange peel oil                                                                         +          +       +     +     weak                                 concentrate                                                                   according to                                                                  Example 1                                                                     Lemon peel oil                                                                          +          +       +     +     weak                                 concentrate                                                                   according to                                                                  Example 3                                                                     ______________________________________                                    

It will be understood that the above description of the presentinvention is susceptible to various modifications, changes andadaptations, and the same are intended to be comprehended within themeaning and range of equivalents of the appended claims.

What is claimed is:
 1. Concentrate of natrual citrus oil which retainsits aroma and is stable in storage, comprising:(a) 10 to 90 percent byweight citrus peel oil concentrate produced from cold-pressed citruspeel oil, the peel oil concentrate being obtained by extracting thecold-pressed citrus peel oil with a polar organic solvent to form asolvent extract phase and a raffinate phase, separating the solventextract phase from the raffinate phase, and separating the peel oilconcentrate from the separated solvent extract phase and (b) theremainder essence oil concentrate.
 2. Concentrate of natural citrus oilwhich retains its aroma and is stable in storage, comprising:(a) 10 to95 percent by weight citrus peel oil concentrate produced fromcold-pressed citrus peel oil, the peel oil concentrate being obtained byextracting the cold-pressed citrus peel oil with a polar organic solventto form a solvent extract phase and a raffinate phase, separating thesolvent extract phase from the raffinate phase, and separating the peeloil concentrate from the separaed solvent extract phase and (b)remainder concentrate of an aqueous essence.
 3. Concentrate of naturalcitrus oil which retains its aroma and is stable in storage,comprising:(a) 10 to 90 percent by weight citrus peel oil concentrateproduced from cold-pressed citrus peel oil, the peel oil concentratebeing obtained by extracting the cold-pressed citrus peel oil with apolar organic solvent to form a solvent extract phase and a raffinatephase, separating the solvent extract phase from the raffinate phase,and separating the peel oil concentrate from the separated solventextract phase and (b) 5 to 85 percent by weight essence oil concentrate,and (c) 5 to 85 percent by weight concentrate of an aqueous essence. 4.A process for producing a concentrate of natural citrus oil whichretains its aroma and is stable in storage comprising: forming a mixturecontaining 10 to 95 percent by weight citrus peel oil concentrate andthe remainder being one or more ingredients selected from the groupconsisting of essence oil concentrate and concentrate of an aqueousessence, wherein the peel oil concentrate is obtained by extracting thecold-pressed citrus peel oil with a polar organic solvent to form asolvent extract phase and a raffinate phase, separating the solventextract phase from the raffinate phase, and separating oil concentratefrom the separated solvent extract phase.